Relay apparatus



April 2, 1963 N. LEE 3,084,312

RELAY APPARATUS Filed Jan. 26, 1960 lNvENToR Noam: LEE.

United States Patent RELAY APPARATUS Norman Lee, Allesley, Coventry, England, assignor to The Keelavite Company Limited, Aliesi'ey, Coventry,

England, a company of Great Britain Filed Jan. 26, 1960, Ser. No. 5,092 Claims priority, application Great Britain Feb. 12, 1959 4 Claims. (Cl. 317-458) This invention relates to control apparatus including a magnetic relay device.

According to one aspect of the present invention the control apparatus includes a magnetic relay device comprising a magnetic circuit including two separable parts one of which is formed for connection to operating means so that the force applied by such means tends to separate the separable parts, and means responsive to the change in magnetic flux in the magnetic circuit when the parts are separated which are arranged to operate indicating or other apparatus.

According to another aspect of the present invention the control apparatus includes a magnetic relay device comprising a magnetic circuit including two movable parts which are independently movable from their normal positions in a direction to open the magnetic circuit, one of such parts being arranged for connection to operating means subject to a variable force tending to move the part in a direction to open the magnetic circuit while the other part is connected to means for operating indicating or other apparatus and has a continuous force applied to it tending to move it in a direction to open the magnetic circuit and such that when both the movable parts are in their normal positions to close the magnetic circuit the second movable part is maintained by a magnetic force in such normal position, whereas when the first movable part is moved by the variable force to open the magnetic circuit the resultant reduction in magnetic fiux in the magnetic circuit is such that the second movable part is automatically moved by the continuously applied force to operate the indicating or other apparatus.

The term magnetic circuit as used herein is intended to cover a circuit comprising at least two parts of magnetizable material, one at least of which is a magnet arranged so that when in a closed condition they make a flux-carrying circuit which is opened if and when they are moved apart, the term opened being used herein to refer to a movement which substantially reduces the magnetic flux in the circuit.

The control apparatus as set forth may include a chamber arranged to be connected to a source of fluid pressure and provided with a movable wall arranged to be movable with variations in said pressure, one of the two separable parts of the magnetic relay device being connected to the movable wall, so that when the fluid pressure reaches a predetermined value the parts separate to cause a change in the magnetic flux in the magnetic circuit.

In this arrangement the magnetic circuit may include a permanent magnet constituting one of the separable parts and carried by the movable wall, and a pair of arms constituting the other separable part extended through a relatively rigid part of the wall of the chamber, the magnet normally extending between the inner ends of the arms while'a bridge piece of magnetizable material is arranged to extend between the outer ends of the arms and has associated with it biassing means tending to sep arate it from the outer ends of the arms, movement of the bridge piece away from the ends of the arms causing operation of the indicating or other apparatus.

Manually operated means are preferably included for re-setting the apparatus by returning the bridge piece into engagement with the outer ends of the arms. Alternatively the movement of the bridge piece away from the ends of the arms may be limited by a stop device so that when the magnet returns into engagement with the inner ends of the arms the flux in the magnetic circuit causes the automatic return of the bridge piece into engagement with the outer ends of the arms.

In a convenient arrangement the movable wall constitutes a partition between two chambers arranged for connection respectively to sources of fluid at different pressures, and the chambers are connected respectively to the upstream and downstream sides of filtering apparatus of the pervious wall type.

The term filtering apparatus of the pervious wall type is used herein to define filtering apparatus of the type in which the fluid to be filtered is caused to how through passages of small cross sectional area in a filtering wall, whetherof the kind comprising a fibrous woven or like material and/or perforated metal or gauze, and/or of the metal plate or similar type.

Preferably the chamber containing one of the separable parts of the magnetic relay is connected to the fluid flow system by a passage in which is housed a magnetic filter.

The invention may be performed in various ways but one particular application in which the magnetic relay is usedin pressure sensitive apparatus will now be described by way of example with reference to the accompanying drawing.

Certain types of hydraulic circuit sometimes include a fine filter of the pervious wall type often referred to as a micro filter, through which the liquid is usually pumped at considerable pressure, and it is desirable that when the pressure drop across the filter, whether the downstream side of the filter be at atmospheric pressure or not, reaches a predetermined value due to the accumulation of dirt on or in the filter, the operation of the apparatus should be automatically stopped or a signal should be given to warn an operator that remedial measures should be taken.

The embodiment of the invention shown in the drawing, and now to be described comprises control apparatus arranged to sense the pressure drop across a filter of the type set forth and when it reaches a predetermined critical value to'cause operation of indicating or other apparatus.

The apparatus comprises a casing 1 formed to provide two separate compartments completely sealed from one another by a dividing wall 2, one housing a pressuresensitive device indicated generally at 3 (and referred to as the hydraulic compartment 4) and the other containing electrical components indicated generally at 5 (andreferred to as the electrical compartment 6). The pressure-sensitive device 3 is in the form of a flexible bellows 7 one end of which carries a movable wall 8' closing that end while its other end is connected in a'fiuid-tight manner to an internal flange 9 formed by the inner part of an annular plate 10 the outer part of which is sealed between two parts of the wall of the compartment so that the compartment is divided into two chambers 11 and 12 by the-bellows 7, the end wall 8 and the plate. 10. A spring l3v is provided within the bellows 7 one end of which bears against a shoulder on the movable wall 8 while its other end bears on an abutment disc 14 on the end or" an adjusting rod 15. The adjusting rod has a screwthreaded part 16 which passes through a screwthreaded bore 17 in the end of the hydraulic compartment 4 remote from the electrical compartment 6 and is provided with an adjusting knob, head or the like 18 and a lock-nut 19 on its outer end.

The two chambers 11 and 12 of the compartment 4 containing the bellows 7 are arranged to be connected respectively to opposite sides of a filter indicated at 29 through passages 22, 23 so that the bellows 7 and the movable wall 8 are subject to the pressure drop across the filter with the higher pressure transmitted to the chamber 11 adjacent to the electrical compartment 6 and therefore acting on the movablewall 8 against the action of the spring 13 within the bellows 7.

Extending through the dividing wall 2 between the hydraulic and electrical compartments and completely sealed therein are a pair of rods 24, 25 of soft iron orlike material of high magnetic permeability and low magnetic retentivity. The ends of these rods which project into the hydraulic compartment 4 normally engage respectively the opposite ends of a permanent bar magnet 26 secured to the movable wall 8 carried by the bellows 7. The ends of the two rods 24, 25 which project into the electrical compartment 6 are normally engaged by a bar 2 7 also of soft iron or other material of high magnetic permeability and low magnetic retentivity, and the rods 24, 25 the bar 27 and the magnet 26 thus normally constitute a magnetic circuit which is closed when the magnet 26 and the bar 27 are in engagement with the ends of the rods. The bar 27 is pivotally mounted at its center on one end of a lever 28 and biased away from the ends of the rods by a small compression spring 30 one end of which bears on the bar in the region oi the pivot of connection to the lever 28 while the other end of the spring bears on the dividing wall 2 between the two compartments 4 and 6. t

The other end of the lever 28 is pivoted to the wall of the electrical compartment 6 at 31 and is arranged to operate a micro-switch 32 when, under the action of the compression spring 30, the bar 27 is moved away from the ends of the rods 24, 25. I

The operation of the device is as follows. Normally when the difference of pressure respectively in the two chambers 11 and 12 of the hydraulic compartment 4 is below a predetermined value the permanent magnet 26 is maintained by magnetic flux in contact with the adjacent ends of the two rods 24, 25 and the magnetic flux then maintains the bar 27 in contact with the other ends of the two rods against the action of the compression spring 30 so that a magnetic circuit is completed by the rods, the magnet and the bar. As the pressure in the chamber 11 of the hydraulic compartment increases relatively to that in the other chamer 12 of the hydraulic compartment the force on the movable wall 8 tending to separate the magnet 26 firom the adjacent ends of the rods 24, 25 increases until it exceeds the opposing force due to attraction of the magnet to the rods plus that exerted by the spring 13 within the bellows 7, whereupon the magnet 26 moves with a snap action out of engagement with the adjacent ends of the rods and the continuity of the magnetic circuit is thus broken. The reduction in magnetic flux in the magnetic circuit thus caused is such that the compression spring 30' is now ableto move the bar 27 away from the adjacent ends of the rods, which it therefore does similarly with a snap action, and the microswitch 32 is operated to provide an appropriate electrical signal which can be used for indicating purposes or to operate appropriate control apparatus not shown. Since the spring 13 within the bellows tends always to return the movable wall and the magnet to their original position, it will be appreciated that when the difference in pressure is again reduced to an appropriate value the magnet 26 will be returned into engagement with the adjacent ends of the rods 24, 25.

A manual push button 33 is included to return the bar 27 into engagement with the other end of the rods, or the arrangement may be such that when the magnet 26 is returned into engagement with its adjacent ends of the rods 24, the flux in the magnetic circuit becomes such as automatically to draw the bar into engagement with the other ends of the rods so that automatic seating is effected. To limit the movement of the lever 28, and thus the bar 27 an adjustable stop screw 34 is provided.

in order to prevent magnetic material which may be in the fluid from the pressure side of the filter 20 firom y reaching the parts of the magnetic circuit within the hydraulic chamber 11, a magnetic filter 35 is provided in the passage 22 which acts to collect any such materials from the fluid in the passage.

What I claim as my invention and desire to secure by Letters Patent is:

1. Control apparatus comprising a pressure chamber including a rigid Wall and a movable wall, passage means for connecting said pressure chamber to a source of fluid pressure, said movable wall being moved by variations in the pressure of fluid supplied to said chamber through said passage means, parts formed of magnetic material, at least one of which is permanently magnetized, said parts constituting a magnetic circuit and comprising a pair of spaced arms passing through said rigid wall and inner and outer bridge pieces arranged to abut respectively the ends of the arms in said chamber and the ends of the arms outside said chamber, said inner bridge piece being connected to said movable wall for movement into and out of engagement with the adjacent ends of said arms, and

operating means supporting said outer bridge piece for i movement into and out of contact with the ends of said arms outside said chamber and including biasing means exerting a force tending to move said outer bridge piece out of contact with said ends of said arms outside said chamber.

2. Control apparatus as claimed in claim 1 in which said movable wall constitutes a partition between said pressure chamber and a second chamber and passage means are provided for connecting said second chamber to a second source of fluid pressure.

3. Control apparatus as claimed in claim 1 including manually-operated means to return said outer bridge piece into engagement with the ends of said arms outside said chamber.

4. Control apparatus as claimed in claim 1 including a stop device limiting movement of said outer bridge piece away from the ends of said arms outside said chamber to a distance from which said bridge piece automatically returns into engagement with said ends of said arms on the return of said inner bridge piece into engagement with the ends of said arms in said chamber.

References Cited in the file of this patent UNITED STATES PATENTS 2,548,581 Bigelow Apr. 10, 1951 2,648,741 Starbird Aug. 11, 1953 2,690,713 Urmann et al. Oct. 5, 1954 2,757,801 Muggli et a1 Aug. 7, 1956 2,782,278 Peters Feb. 19,1957 2,809,248 Frakes Oct. 8, 1957 2,814,687 Forwald Nov. 26, 1957 2,814,689 Roche Nov. 26, 1957 2,847,528 Combs Aug. 12, 1958 2,856,481 Ernst Oct. 14, 1958 2,885,506 Anderson May 5, 1959 2,887,546 Hatfield et al. May 19, 1959 2,892, 05 1 Moore June 23, 1959 2,922,002 Gilman Jan. 19, 1960 2,942,572 Pall June 28, 1960 

1. CONTROL APPARATUS COMPRISING A PRESSURE CHAMBER INCLUDING A RIGID WALL AND A MOVABLE WALL, PASSAGE MEANS FOR CONNECTING SAID PRESSURE CHAMBER TO A SOURCE OF FLUID PRESSURE, SAID MOVABLE WALL BEING MOVED BY VARIATIONS IN THE PRESSURE OF FLUID SUPPLIED TO SAID CHAMBER THROUGH SAID PASSAGE MEANS, PARTS FORMED OF MAGNETIC MATERIAL, AT LEAST ONE OF WHICH IS PERMANENTLY MAGNETIZED, SAID PARTS CONSTITUTING A MAGNETIC CIRCUIT AND COMPRISING A PAIR OF SPACED ARMS PASSING THROUGH SAID RIGID WALL AND INNER AND OUTER BRIDGE PIECES ARRANGED TO ABUT RESPECTIVELY THE ENDS OF THE ARMS IN SAID CHAMBER AND THE ENDS OF THE ARMS OUTSIDE SAID CHAMBER, SAID INNER BRIDGE PIECE BEING CONNECTED TO SAID MOVABLE WALL FOR MOVEMENT INTO AND OUT OF ENGAGEMENT WITH THE ADJACENT ENDS OF SAID ARMS, AND OPERATING MEANS SUPPORTING SAID OUTER BRIDGE PIECE FOR MOVEMENT INTO AND OUT OF CONTACT WITH THE ENDS OF SAID ARMS OUTSIDE SAID CHAMBER AND INCLUDING BIASING MEANS EXERTING A FORCE TENDING TO MOVE SAID OUTER BRIDGE PIECE OUT OF CONTACT WITH SAID ENDS OF SAID ARMS OUTSIDE SAID CHAMBER. 